Method of coating metals



Patented May 27, 1 930 Qumran STATES PATE OFFICE.

EDWIN RJMILLRING, 01 NEW YORK, N. Y2, ASSIGNOB T0 AMERICAN MACHINE & FOUN- v DRY COMPANY, CORPORATION OE NEW JERSEY METHOD OF COATING METALS No Drawing. 7

v This invention relates to the covering of metals with a metallic coat to protect them from the elements of oxidation and corrosion, such as exposure to the atmosphere, water, sea water, salt solutions, acids, chemicals, in dustrial gases, etc., and the invention is a plicable'to the treatment of various meta s, such as iron, steel, cooper, brass, etc., in order to give them a protective coating.

The objects of the invention are to produce a-protective coating which will be of the requisite thickness, hardness, and continuity, to withstand the effects of oxidation, corrosion, and abrasion, andthe invention consists primarily in a method of procedure involvin the application to the metal to be protecte of a protective coating alloy in super-cooled or metastable condition.

The invention consists also in the application of such super-cooled protective alloy to metals having a previously applied protective base coat, in order to thicken such base coat, fill up and cover breaks or pin holes or other defects therein, and thus produce con.- tinuity of the-same; in some cases to produce a secondary metz'lillic coat actually superimposed upon the base coat, a result not obtained by other methods on account of the alloying action between the first and second coats; and to provide an outer hard coat well adapted to prevent abrasion.

' The invention consists also of the improved alloy bath employed'in carrying themethod into effect.

It is knownthat certain metallic solutions, as well as non metallic solutions, .ean exist in the liquid state at a considerably lower temperature than that at which the solid,

this metastable condition is rather pro' nounced. It is also known that, when certain alloys have been brought to a perfectly homogeneousliquid solution by'the application of heat, and are allowed to cool, at a certain temperature one or more components of the al- 7 Application filed July 21,

1923. Serial No. 653,022.

loys begins to freeze out. This temperature point is known as the liquidius for the articular alloy. When the. alloy is allowe to cool further, it still exists in a partly solid crystalliz'ing out increases the thickness of the coat and consequently its protective value,

and it also increases the continuity and hardness of the coat, so that the efiect is to produce a coating possessing all of the properties which will best serve the objects and advantages sought. It is such a super-cooled alloy that I employ in the treatment of metals to apply a protective coating, the said alloy being either applied directly to uncoated metals, or applied as a second coating to metals having a previously applied metallic base coat.

' It is of course recognized that, in the case or alloys not possessing the above mentioned properties, or in the case of alloys possessing these properties under conditions other than herein described, such as-at a higher temperature' than the liquidius of the alloy, or at such a temperature as when the alloy is a. perfectly homogeneous stable liquid, the advantages sought would not be obtained, and

the coating so obtained would be much thin ner and less continuous, thus possessing the faults of the usual hot dipping process.

Examples of two allo s, electro-positive to iron, and exhibiting t e above mentioned properties of a super-cooled solution are the following: Y I r 1. Antimony 12.5%, bismuth 10.0%, lead 2. Antimony 12.5%, cadmium;5.0%,,lead

having the above mentioned properties of a su -coled solution but electro-negative to iron: Zinc 18%, cadmium 82%.

In practicing my invention, in'applying a protective coating directly to uncoated metal, when employing an alloy for instance of antimony, lead and bismuth, the metal to be protected is first cleansed in any suitable and appropriate manner, as by heat treatment, mechanical, chemical, or electrical means, and is fluxed with a suitable flux, such as zinc chloride or the'like. The alloy bath is now prepared,ethe proportion of antimony not to u exceed bismuth not to exceed 40%, and

the remainder lead; but I prefer that the ingradients shall be in the proportions first mentioned viz. 12.5% antimony, math, and 57.5 lead. These in dients are reduced to molten condition an heated to a temperature of approximately 450 C. in order to bring about their complete fusion and to produce aitrue solution, thereby producing an alloy having a melting point o approximately 232 0. The temperature of the bath is then lowered sufliciently to bring it to a super-cools: tlrlonditio'n and producingt a su r-coo a o eproper ies he rzinbefore deszribed. The cleansed and fluxed metal is now immersed in this supercooled bath, and receives on its surface a coating of the alloy, and on bein withdrawn from the bath, it ma be quenc ed in water or oil or othhr suitab e quenching medium.

When em loying an allo of antimony, cadmium 'an lead, or of ca ium andzinc, as in the examples above given which alloys have melting ints respective y of 240 C. and 270 C.,'t 0 method of procedure would be the same'as that just described, the bath being firstheated to a temperature to produce a true solution of the ingredients, and then reduced'in tem rature to bring about its super-cooled con 'tion.

Other alloys may be employed which possess the roperties of a super-cooled solution, wi out departing from the l im1ts of my invention, those above given being merelfyby way of example, and such as havebeen ound in practice to answer (1 the ends to be attained,

n the practice of my invention when apply' a protective coating to metals havmg previously appiied metallic base coat, the base coat may galvanized tin, lead, copper or other metals or alloys, and the coat may be applied by the usual methods practised in the art, such ing, electro-plating, etc. The metal wit the base coat applied, and after the base coat has set, is immersed in a super-cooled alloy bath prepared accordance with my invention as hereinbeioredescribed," with the re- .sult that the base\coat will receive on sur- 1 i faceaeoating ofthis alloy, which being de- The following is an example of an alloy .the first and second coats.

10% bismuth super-cooled conditioni a protective coverin ossessing in marke to a satisfactofly immersing the metal to as by hot dipping, s rayposited under the super-cooled conditions described, will have the effect of-increasing the thickness of the base coat, and will increase its hardness,'and will cover up such defects or breaks or. pin holes as may exist in the base coat, and in this way will bring about a perfect continuity of the protective coating. In some cases t e apphcation of the supercooled alloy to the previously coated metal, actually superimposes upon the base coat, a secondary coat, which could not bebrought about by other means on account of the alloying action which would take place between While the supercooled alloy may be applied directl to the base coat after t e latter has set as a ove described, yet it may in some cases and under certain conditions be desirable to quench the base .coat with or immerse the same in a e'suitable flux solution to render the surface receptive to the super-cooled alloy.

While in the case of the a plication of a. super-cooledalloy toprevious y coated metal, 7 the base coat may be composed of various kinds of metals or alloys of the same as hereinbefore mentioned, I have found that a very satisfactory coating may be obtained mac-- cordance' with my invention by applying a super-cooled alloy of lead, antimony and bisor of lead, cadmium and antimony, to a base coat composed of-lead, phosphorus and tin wherein the lead is'ina proportion greatly redominatingthe other ingredients, and suc 4 with ninety-seven (97) 'unds of lead three ('3) pounds or less of p osphortin. A base coat of these particular ingredients has been found to adhere 've tenaciously and closely to the metal to whic it is applied, on account of the presence of the phosphorus therein,

and by applying thereto a coating-alloy infor the metal is secure degree the properties a v6 described with res t to thickness, hardness and continuity an the-co uent resistance'to oxidation, corrosion and a rasion..

Having thus described my invention, what 'I claim 1s:

1. The method of covering metal with a protective metal coating, which consists in applying to the metal a coating-alloy in su r-cooled condition.

2. The method of covering metal with a rotective metal coating, which consists in coated in a supercooled bath of an alloy.

as would be produced by mixing 3. The method of preparing a coating bath Q tor metal, which consists in providing an alloy bath heated to a temperature at which the ingredients are in true solution, and reducing cool t e same to bring it to a metastable condition. p 4. The method of covering metal with a.

the temperature of the bath to superprotective metal coating, which consists in applying a primary metal coating thereto, allowing said coating to set, and immersing the coated metal in a super-cooled alloy bath.

5. The method of covering metal with a protective metal coating, which consists in applying a primary metal coating thereto,

allowing said coating to set, and immersing the coated metal in a super-cooled bath containing antimony and lead.

6. The method of coating metal with a protective metal coating, which consists in applying a primary metal coating thereto, allowing said coating to set, and immersing the metal in a super-cooled bath of an alloy alloy of antimony, bismuth and lead.

7. The method of coating metal with a protective metal coating, which consists in applying a primary metal coating thereto, allowing said coating to set, and immersing the coated m tal in a super-cooled bath of an alloy of antimony, bismuth and lead in substantially the proportions specified. I

8. The method of coating metal with a protective metal coating, which consists in applying a primary metal coating thereto, allowing said coating to set, and immersing the, coated metal in a super-cooled bath of an alloy of 12.5% of antimony, 10% of hismuth, and 77.5% of lead.

In testimony whereof, I have afiixed my signature hereto.

EDWIN R. MILLRING. 

